Effect of reverse micelles on the Rose Bengal-sensitized photo-oxidation of 1- and 2-hydroxynaphthalenes

Abstract

Benzylhexadecyl dimethylammonium chloride (BHDC) and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) water-in-oil micro-emulsions were employed to study the influence of medium heterogeneity on singlet molecular oxygen [O(2)((1)Delta(g))]-mediated degradation of 1-hydroxynaphthalene (1-OHN) and 2-hydroxynaphthalene (2-OHN) in their naphthoate form. The kinetic study in the micellar system, that was considered as a closer model for the environment of contaminants in natural polluted waters, consisted of a comparative work with the process in homogeneous solution, by varying surfactant structure and water content of the micro-emulsion. While it is known that 1-OHN and 2-OHN are rapidly and efficiently photo-oxidised in aqueous medium, time-resolved phosphorescence detection of O(2)((1)Delta(g)) and stationary photolysis experiments demonstrate that both the values for the overall and reactive rate constants for the quenching of O(2)((1)Delta(g)) and the photo-oxidation efficiencies are lowered in BHDC micelles, whereas the photo-oxidative process in AOT micro-emulsions was totally inhibited. Results are interpreted and discussed on the basis of different locations of the probe in the micellar environment.

Triplet quantum yields in light-scattering powder samples measured by laser-induced optoacoustic spectroscopy (LIOAS)

“…The photophysics of dyes in microheterogeneous media (micelles, liposomes, membranes, polymers, etc.) impacts on various fields, such as photomedicine, [1][2][3] inactivation of microorganisms, 4,5 abatement of organic pollutants, 6,7 and so forth. Applications based on organized systems composed of a dye anchored to nanoparticles or incorporated into a solid matrix received particular attention in connection to photodynamic therapy, [8][9][10] heterogeneous photocatalysis [11][12][13] and the development of sensors, transducers and solar cells.…”

Influence of pH and micellar systems on the sensitized photo‐oxidation of bovine serum albumin

“…The respective value of k t decreases as the solvent polarity decreases . It is known that the macroscopic dielectric constant in the interior of the water pool in RMs is lower than that of free water and increases with the increase of the W value for the same micellar system . This change in the micro‐polarity could explain the kinetic data obtained.…”

“…The observed photo‐stability of BSA can be attributed to the fact that the exited encounter complex with partial charge‐transfer character between the reactive species, O 2 ( 1 △ g ), and substrates like Tyr and Trp, is affected by the polarity of the micro‐environment. The respective value of k t decreases as the solvent polarity decreases . It is known that the macroscopic dielectric constant in the interior of the water pool in RMs is lower than that of free water and increases with the increase of the W value for the same micellar system .…”

A Kinetic Study of the Photodynamic Effect on Tryptophan Methyl Ester and Tryptophan Octyl Ester in DOPC Vesicles

“…It was already established that the O 2 ( 1 Δ g )‐mediated oxidation of some compounds (Q), such as phenols and indoles, including tyr and trp (43–46) occurs through an excited encounter complex [Q ... O 2 ( 1 Δ g )] where the reactive component is governed by a charge‐transfer‐mediated mechanism which is favored by increasing the solvent polarity. However, when O 2 ( 1 Δ g ) is generated by RB at the interface or by PN at the lipidic region and the trpD is totally associated to the membrane ([DOPC] = 1 mg mL −1 ), there is an increase in the k r,app values as compared with that obtained in pure water.…”